Catch ConnectionError when Docker isn't running (#66)

Author: tobywf

python/rpdk/python/codegen.py

@@ -7,6 +7,7 @@
 
 import docker
 from docker.errors import APIError, ContainerError, ImageLoadError
+from requests.exceptions import ConnectionError as RequestsConnectionError
 from rpdk.core.data_loaders import resource_stream
 from rpdk.core.exceptions import DownstreamError, SysExitRecommendedError
 from rpdk.core.init import input_with_validation
@@ -249,6 +250,15 @@ def _docker_build(cls, external_path):
                 volumes=volumes,
                 stream=True,
             )
+        except RequestsConnectionError as e:
+            # it seems quite hard to reliably extract the cause from
+            # ConnectionError. we replace it with a friendlier error message
+            # and preserve the cause for debug traceback
+            cause = RequestsConnectionError(
+                "Could not connect to docker - is it running?"
+            )
+            cause.__cause__ = e
+            raise DownstreamError("Error running docker build") from cause
         except (ContainerError, ImageLoadError, APIError) as e:
             raise DownstreamError("Error running docker build") from e
         LOG.debug("Build running. Output:")

tests/plugin/codegen_test.py

@@ -9,6 +9,7 @@
 import pytest
 
 from docker.errors import APIError, ContainerError, ImageLoadError
+from requests.exceptions import ConnectionError as RequestsConnectionError
 from rpdk.core.exceptions import DownstreamError
 from rpdk.core.project import Project
 from rpdk.python.codegen import (
@@ -252,6 +253,9 @@ def test__docker_build_good_path(plugin, tmp_path):
         lambda: ContainerError("abcde", 255, "/bin/false", "image", ""),
         ImageLoadError,
         lambda: APIError("500"),
+        lambda: RequestsConnectionError(
+            "Connection aborted.", ConnectionRefusedError(61, "Connection refused")
+        ),
     ],
 )
 def test__docker_build_bad_path(plugin, tmp_path, exception):